Saw blades made of wire or cable have been used for many years in the stone cutting industry in the shaping of quarried blocks of marble and granite. U.S. Pat. No. 1,306,636 taught the use of a wire cable with one strand projecting slightly beyond the surface of the cable, and being an abrasive cord.
U.S. Pat. No. 2,123,619 suggested the use of three triangular wires in a cable or three rectangular wires, with the apices retained together as the three wires were twisted into a cable so as to provide a maximum space between the wires for containing the abrasive slurry used to perform much of the stone cutting.
U.S. Pat. No. Re. 24,660 suggested the use of two wires twisted into a cable, with each wire being a half-round and a half-square cross section in order to have large interstices for the slurry. U.S. Pat. No. 3,150,470 suggested a braided wire cable with diamond particles embedded thereon. U.S. Pat. No. 4,015,931 suggested a plurality such as seven wires deformed into a circular shape and then with protruding, bonded abrasive particles on the cable. U.S. Pat. No. 4,580,545 suggested the use of two square wires twisted into a cable in a single helical direction, and with the two wires having opposite twists relative to each other.
U.S. Pat. No. 3,257,792 disclosed a two-wire cable, with each wire deformed from a round shape into a generally elliptical shape.
Other objects besides stones have been cut by a twisted wire cable. A type of wood-cutting endless loop band saw was suggested in U.S. Pat. No. 152,970 wherein teeth were cut on one edge of a narrow bar of steel and then the bar twisted so that the teeth were in a spiral around the completed blade. A similar construction for a non-continous loop was disclosed in U.S. Pat. Nos. 2,988,118 and 2,749,949. A relatively stiff saw blade with a handle at one end but with a somewhat similar construction was suggested in U.S. Pat. No. 2,101,583.
U.S. Pat. No. 1,543,195 suggested a type of medical saw blade with four piano wires first twisted in pairs in one direction, the two pairs being then twisted together in the opposite direction.
U.S. Pat. No. 3,495,590 disclosed another type of medical saw for removing casts and had a single wire on which was formed a helical projecting tooth.
A surgeon's Gigli saw is a flexible cable which may be inserted into a person or animal through an opening in the flesh and wrapped around a bone, then pulled alternately on opposite ends to abrasively cut through the bone. Such a saw has a considerably different structure, operation, and result from the stone cutting saws. In the stone cutting saws, one finds a continuous loop cable which travels at high speed, e.g., 4500 feet per minute, and moves only unidirectionally. A typical construction is to reverse the direction of twist of the wires in the cable periodically, e.g., every 50 feet, so as to keep the kerf of the cut in the stone block as nearly planar as possible. Further, such stone cutting wire cables do not have much flex considering their diameter because they travel over large diameter pulleys and there is not much flex at the area of cutting on the block of stone. Further, such wire cables cut primarily by the use of a slurry of silicon carbide or the like, so such cables need large interstices to carry the slurry into the kerf. Also, where such wire cables have pockets to receive abrasive particles bonded to the cable, such pockets materially weaken the wire cable.
The surgeon's Gigli saw, on the other hand, is one which needs to be of much smaller cable, and is bent at about a 180-degree bend around the bone to be cut, so it must be quite flexible. Also, such saws must have high tensile strength so that they will not break during the surgery, either from excessive tensile force or poor flexion capabilities. The saws must also have the proper cutting rate because if the cutting rate is too slow, the operation will take too long and also the surgeon may get too tired before the bone is severed. If the cutting rate is too high, the saw may jam in the kerf and it may be broken by the surgeon in trying to pull it loose. Further, the Gigli saw should have a uniform diameter so that there is a smooth cut and the saw will not bind in the kerf. Accordingly, it is desired to have a saw with a maximum amount of material removal per stroke, and also a saw which will cut equally well in each direction of the stroke. The saw must have good fatigue life so that the bone may be cut using only a single Gigli saw rather than using two or three in succession. The saw need not have extended life, however, because they are discarded after one use, since the saw teeth contain bits of flesh and bone and it is impractical to try to clean and sterilize them.
Accordingly, the problem to be solved is how to construct a surgeon's Gigli saw which will produce a smooth cut, not bind in the kerf, have a maximum amount of material removal per stroke, and have good tension, flexion, and cutting properties.
This problem is solved by a surgeon's Gigli saw comprising, in combination, a cable comprising a plurality of strands twisted together in a first rotational direction, at least one strand of said cable having been previously twisted along its own axis in the opposite rotational direction from that of said cable, and each strand comprising a plurality of wires substantially coined together into a generally polygonal cross-sectional shape.
The problem is further solved by the method of manufacture of a surgeon's Gigli saw comprising the steps of providing a plurality of individual wires, passing said plurality of wires as a bundle through a coining stand to form a strand of said wires substantially coined into a polygonal cross-sectional shape, twisting at least one of said strands in a first rotational direction, providing a plurality of such strands, and twisting said plurality of strands in the opposite rotational direction into a cable.
Accordingly, an object of the invention is to provide a Gigli saw with improved tension, flexion, and cutting characteristics.
Another object of the invention is to provide a Gigli saw with a substantially uniform diameter to obtain a smooth cut and prevent binding in the kerf.
Still another object of the invention is to provide a method of making a Gigli saw which is simple and economical so that the saws may economically be discarded after one use.
A further object of the invention is to provide a Gigli saw with a plurality of substantially square strands twisted into a cable and each strand being coined into a polygonal shape from a plurality of wires.